1. Field of the Invention
The present invention relates to a printing machine which conducts printing while winding out labels wound in a roll with a backing paper, or continuous tags wound in a roll, or receipt paper wound in a roll, or the like (hereinafter, referred to generally as "rolled printing paper").
2. Description of the Related Art
In order that continuous tags, or the like, wound out from a roll (hereinafter, simply referred to "printing paper") are guided correctly to the printing position of a printing machine, and that printing is conducted at the correct position on the printing paper with good timing, a printing machine is provided with a printing paper width guide, which is adjustable according to the width dimension of the paper, and a position sensor for detecting a prescribed position of the printing paper, located in the conveyance path of the printing paper.
Since the position detection sensor will pose an obstacle to paper setting if it is positioned above the conveyance path of the printing paper, it is located either beneath the conveyance path, or to one side thereof. Therefore, the composition becomes complex and it becomes impossible to detect the position of the printing paper accurately.
For example, when printing on tags, string attachment holes located centrally in the transverse direction of the tags may be detected to locate the printing position, but usually, even if the tag width dimensions are changed, this string attachment hole will always be in a central transverse position. Consequently, when the width of the printing paper changes, the central position of the printing paper with respect to the printing machine also changes, and therefore it is necessary to move the positional sensor at the same time as moving the printing paper width guide in accordance with the printing paper width.
Moreover, since the printing paper width guide and the position sensor must be positioned such that they project into the paper conveyance path, they present an obstacle when the printing paper is set at the start of the printing operation. Because the paper width guide can be adjusted in accordance with the width of the printing paper, it does not present a significant obstacle if it is set to maximum width in advance, but since the position sensor should desirably be located in a position where it can detect the central portion of the printing paper, it presents a particular obstacle.
A printing machine is also provided with guide rollers for guiding the printing paper accurately into the paper conveyance path. Furthermore, a paper sensor for detecting the end of the printing paper is also provided, in order to halt operation of the printing machine when the whole roll has been wound out and the printing paper has run out.
However, such guide rollers and paper sensors are located close to the paper conveyance path and when fresh printing paper is loaded into the printing machine, a problem arises in that the printing paper must be inserted into a narrow gap between the guide roller and paper sensor and the paper conveyance path.
In Japanese Patent Laid-open No. Hei. 8-58168, a paper holder supported by arms on either side is installed rotatably in a frame, such that the printing paper sensor can project into and withdraw from the paper conveyance path with the rotation of the head holder. Accordingly, it seems this prior art has resolved the problems associated with loading new printing paper into the printing machine.
However, even in this printing machine, the leading end of a new roll of printing paper must be inserted inbetween the arms positioned on either side, and therefore the paper setting operation is still difficult. Moreover, since the rolled printing paper is inserted from the roll directly inbetween the head holder and platen, no guide roller is provided to keep the position of the printing paper stable at this point.